Digital Conversion
Methodology: Quality Control

To assure high quality digital files, each image will be evaluated
twice. The scanning technician will examine the histogram at
the time of capture and creation of the master file. At random,
the master files are examined by the curator to assure that all
files meet the following criteria:

File Format: Uncompressed TIFF files. A TIFF file is
currently the most flexible file format for long-term storage
of digital images. TIFFs can be turned into any other file formats
you require, for example, JPEGs or GIFs for World Wide Web viewing.

Resolution: The initial scans will be 800ppi uninterpolated,
although resolutions as high as 3175ppi uninterpolated are available.
These higher resolutions are most helpful for very small originals
and images that are heavily used and most important intellectually.

Histogram:

Clipping & Spiking: Histograms offer the best view
of tonal range captured by the scanner and will be examined for
clipping and spiking as well as for the correct setting of white
and black points.

Clipping and spiking result when the white and black points
are not set on true white and black during the set up of the
scan. If white and black are improperly set, everything above
or below those points is "clipped" or registers as
the same tone.

Spiking on the ends of the histogram usually indicates clipping.
This problem also shows up in the image itself as blockage and
pixelization in the shadows and blowouts in the highlights. Acceptable
spikes can occur if the edge of the original negative has lost
emulsion, for example, or the sky holds no detail and is one
tone in the original. Such instances, however, are rare.

Histogram:

White & Black Points: Optimum placement of whites
and blacks is best observed through the histogram, although the
image itself will be examined without the histogram on the screen.
It is important to look at the number value assigned to the brightest
highlight and the darkest shadow. Highlights should not read
a number value higher than 247 and shadows should not be less
than 7 or 8. If these numbers are exceeded the scan must be redone.
This is particularly vital if the original image has a short
dynamic range. The white and black points must not be set on
0 and 255, as this will stretch the dynamic range of the image,
creating gaps in the histograms, and thus unusable scans.

Files failing to meet the above criteria will be rescanned.
No adjustments in PhotoShop or other image manipulation
software will be allowed to correct mistakes made in the scanning
process.

Once the master files pass quality control, the thumbnail
and reference files will be created. The technician will need
to make some adjustments to contrast and possibly cut back frame
edges when creating these trimmed-down files. Because of the
manipulations necessary in PhotoShop to create snappy images
for on-screen viewing, the thumbnails and reference files will
undergo a more limited set of quality control procedures. The
technician will examine the histogram for excessive gaps and
check the shadow areas in the image for pixelization. When the
technician is satisfied that the files will pass quality control,
the curator will examine a random selection and then mark the
files for copy onto the final storage media, CD-ROM.

Digital Conversion
Methodology: Format

The initial scan captured from the original materials, called
the master file, will be an uncompressed TIFF with a resolution
of 800ppi, and approximately 35 MB in size for a grayscale scan
of a 6x8 inch glass plate negative and 100MB for an RGB scan
6x8 inch color originals. Trimmed files will be JPEGs. File names
will remain constant with extensions differentiating thumbnails,
reference, and master files. The reference file will be comprised
of approximately 600 pixels wide with a resolution of 300ppi.
The thumbnail will be approximately 150 pixels wide and have
a resolution of 72ppi.

Master: The file created from the initial scan of the
original material. These digital masters will be burned on CD-ROMs
and put on a refreshment cycle of three years. The archival files
will be used to create the reference files and thumbnails.

Minimum Resolution:

800 pixels per inch

Format:

uncompressed tif

Reference: The full-screen view of the image created
from the archival file. This file will be accessed after a user
selects the thumbnail. The reference files will be used for electronic
access only on the World Wide Web and on the Nebraska State Historical
Society's in-house patron computers.

Resolution:

150ppi (600 pixels wide)

Format:

high quality jpg

Thumbnail: The smallest image file created from the
archival file allowing the user to view several images on the
screen at one time. Selecting a thumbnail prompts the access
of the reference file for that image.

Resolution:

72ppi (150 pixels long dimension)

Format:

high quality jpg

Digital
Conversion Methodology: Production

Hardware:

Creo/Scitex EverSmart Supreme Scanner: The EverSmart
Supreme is a high resolution flatbed scanner that utilizes
an 8000 element, anti-blooming CCD. It scans on both the X and
Y axis enabling extremely high resolution over the entire image
bed.

Creo/Scitex EverSmart Pro Scanner: The EverSmart
Pro is a high resolution flatbed scanner that utilizes
an 8000 element, anti-blooming CCD. It scans on both the X and
Y axis enabling extremely high resolution over the entire image
bed.

Phase One FX Digital Camera: The Phase One FX is a
high end digital scan back camera ideal for capturing digital
images from materials too large for the EverSmart Pro image
bed or too fragile to be placed upside-down on the flatbed scanner.
The FX fits on a Toyo 4x5 view camera.